feat: add boxing module API — GET /box/info and POST /box

- Add box schemas (BoxInfoResponse, BoxSaveRequest, BoxSaveResponse)
- Add box service with ERP view query and save logic (supports many2one append)
- Add box router with GET /box/info and POST /box endpoints
- Register exception handlers for InvalidZongpaiError, ZongpaiNotFoundError, DuplicateBoxItemError
- Update RequestValidationError handler to cover INVALID_BOX_NO and INVALID_QUANTITY
- Add 7 integration tests for box API

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/api/v1/box.py

@@ -0,0 +1,23 @@
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.orm import Session
+
+from app.core.database import get_db
+from app.schemas.box import BoxInfoResponse, BoxSaveRequest, BoxSaveResponse
+from app.services.box_service import get_box_info, save_box_record
+
+router = APIRouter(tags=["boxing"])
+
+
+@router.get("/box/info", response_model=BoxInfoResponse)
+def box_info(
+    zongpai_no: str = Query(..., description="总排号"),
+    db: Session = Depends(get_db),
+):
+    """查询装箱信息：根据总排号查询排产号、数量和已有箱号明细。"""
+    return get_box_info(db, zongpai_no)
+
+
+@router.post("/box", response_model=BoxSaveResponse)
+def create_box(req: BoxSaveRequest, db: Session = Depends(get_db)):
+    """保存装箱记录：将总排号记录到指定箱号中。"""
+    return save_box_record(db, req)